Infrared Sensor Calibration for Semiconductor Emissivity
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Solution Overview
Problem
Conventional methods for cooling high-power semiconductor devices during thermal imaging, such as diamond heat spreaders and sealed fluid chambers, suffer from issues like Newton's rings degrading infrared images and photon absorption/reflectance, making accurate emissivity measurement elusive.
Innovation Solution
A system with an infrared sensor and optical pathway that includes a transmissive window and fluid, where the transmission and emission characteristics of these components are determined and used to calculate the actual photon count from the semiconductor chip, accounting for the effects of the window and fluid on the measured radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a diamond heat spreader is used for cooling, then optical access is maintained, but Newton's rings degrade the infrared image
Solution Approach 1:
A fluid layer is introduced as an intermediary between the diamond heat spreader and the semiconductor device. This fluid layer acts as a mediator that eliminates direct contact between the diamond window and device surface, thereby preventing Newton's rings while maintaining thermal coupling and optical transparency for infrared imaging
Solution Approach 2:
The cooling system is segmented into distinct components: a diamond heat spreader, a fluid layer, and the semiconductor device. This segmentation allows each component to perform its specific function independently - the diamond provides structural support and thermal conduction, the fluid provides thermal coupling without optical interference, and the device being tested remains separate from potential sources of image degradation
2Temperature
If a sealed fluid chamber is used for cooling, then heat removal is facilitated, but the liquid and window mask the actual photon count from the chip
Solution Approach 1:
The optical properties of the fluid and window materials are carefully selected and characterized to minimize absorption and reflection in the infrared spectrum. By changing the material parameters (selecting specific fluids and window materials with known transmission characteristics), the system achieves both effective heat removal and accurate photon detection
Solution Approach 2:
The system incorporates calibration procedures where the transmission and emission characteristics of the window and fluid are determined and used to correct the measured radiation. This feedback mechanism allows the system to account for and compensate for the absorption and reflection effects, recovering the actual photon count from the semiconductor device
3Temperature
If conventional cooling methods are used, then heat is removed, but accurate emissivity measurement becomes elusive due to absorption and reflection
Solution Approach 1:
The system performs calibration measurements to determine the transmission and emission characteristics of all components in the optical path (window and fluid). These measured parameters are then used as feedback to correct the thermal imaging measurements, allowing accurate calculation of the semiconductor device's emissivity despite the presence of cooling components
Solution Approach 2:
The system replaces conventional opaque cooling methods with an infrared-transparent cooling system using specially selected fluids and window materials. This substitution allows the optical measurement system to see through the cooling components, enabling simultaneous thermal management and accurate emissivity measurement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate determination of the semiconductor chip's emissivity by accounting for the transmission and emission of the transmissive window and fluid, effectively overcoming the limitations of previous cooling methods and providing clear optical access for thermal imaging.
Implementation Method 1
a transmissive window and fluid in the optical pathway between the infrared sensor and the semiconductor chip, each having a known transmission and emission
Implementation Method 2
an infrared emission bw(T) of the transmissive window and an infrared emission bf(T) of the transmissive fluid for at least one temperature
Implementation Method 3
Radiation from the optical pathway is measured with the infrared sensor
Data Source
AI summary
A method includes determining a transmission of a transmissive window and a transmission of a transmissive fluid. In addition, an infrared emission of the transmissive window is determined along with an infrared emission of the transmissive fluid for at least one temperature. In a system that has an infrared sensor and an optical pathway to the infrared sensor, the transmissive window and the transmissive fluid are placed in the optical pathway. A semiconductor chip is placed in the optical pathway proximate the transmissive fluid. Radiation from the optical pathway is measured with the infrared sensor. An emissivity of the semiconductor chip is determined using the measured radiation and the determined transmissions and emissions of the transmissive window and the transmissive fluid.